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If n is a positive integer such that the units (ones)
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15 Sep 2020, 08:39
15 Sep 2020, 08:39
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81% (01:51) correct
18% (00:45) wrong based on 16 sessions
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If n is a positive integer such that the units (ones) digit of \(n^2+4n\) is 7 and the units digit of n is not 7, what is the units digit of n+3?
320 GRE Math Problems
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320 GRE Math Problems
Re: If n is a positive integer such that the units (ones)
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15 Sep 2020, 09:10
15 Sep 2020, 09:10
4
given
\(n^2+4n\) units digit is 7 and units digit of n is 7
by simplifying that n(n+4)
if n is even then units digit won't be odd so neglect 2,4,6,8 and even integers
remaining 1,3,5,9 and other odd integers without units digit 7
if we take 1 then units digit is 5
if we take 3 then units digit is 1
if we take 5 then units digit is 5
if we take 9 then units digit is 7
so n will 9 and odd integers having units digit 9
now units digit of n+3 will be 2(9+3=12)
\(n^2+4n\) units digit is 7 and units digit of n is 7
by simplifying that n(n+4)
if n is even then units digit won't be odd so neglect 2,4,6,8 and even integers
remaining 1,3,5,9 and other odd integers without units digit 7
if we take 1 then units digit is 5
if we take 3 then units digit is 1
if we take 5 then units digit is 5
if we take 9 then units digit is 7
so n will 9 and odd integers having units digit 9
now units digit of n+3 will be 2(9+3=12)
Re: If n is a positive integer such that the units (ones)
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17 Oct 2020, 05:31
17 Oct 2020, 05:31
interesting question!
